How to prevent a clubroot catastrophe

Some recommendations for all scenarios

How to prevent a clubroot catastrophe

The mentality amongst some of our Prairie canola growers is, “I’ll just wait until clubroot shows up and then I will seed a resistant variety.”

Big mistake!

Canola growers whose croplands are free of this destructive disease should be seeding resistant canola varieties right away. Yes, this year. Before clubroot shows up.

I presently handle plant disease and other crop problem questions twelve months a year, for perhaps 50 or more specialist advisors (crop coaches) from Ontario to British Columbia’s Peace Region and down into Montana.

All the advisors’ clients planted clubroot-resistant canola as soon as the seed was available — the old stitch in time saves nine. Nonetheless, I hear from them talk about non-clients who make statements like, “Resistant varieties yield less than susceptible canolas.” Not true.

The resistant types yield the same as the non-resistant and often, depending on the variety, outyield them. This is coffee shop talk not based on any facts. Not planting resistant canola varieties is not even short-term pain for long-term gain. Grow resistant varieties right away.

Another coffee shop untruth is no matter what you do, clubroot will eventually blow onto your cropland from neighbouring infected canola cropland. Not true.

If you grow resistant varieties, a particularly bothersome factor is that some farmers suspect their neighbours have clubroot-infected cropland. If you grow clubroot-resistant varieties, you will not have a problem with them as long as you keep your land free of any and all cruciferous weeds (shepherd’s purse, stinkweed, wild mustard, etc.) and any non-resistant volunteer canola. The blown in, infested dust is not enough inoculum to infest resistant varieties.

How to keep your cropland clubroot-free

Clubroot is a disease of most, if not all, crops related to canola, such as cabbage, stinkweed, shepherd’s purse, radish, etc. In other words, the clubroot fungus or its various strains will infect all members of the cruciferous or cabbage family.

It’s a microscopic soil-borne fungus called Plasmodiophora brassicae. A canola field infested with this fungus may have soil that can have up to 10 million fungus spores per gram. It takes 30 grams to make one ounce.

Have you noticed that if you want to visit a commercial hog or poultry operation you cannot just walk in. You are either denied access or you may have to wash up and wear sterile overalls. This applies even to visiting veterinarians.

You need this mentality to protect your cropland from soil-borne infectious diseases, such as clubroot of canola, soybean cyst nematode, aphanomyces root rot of peas and many other soil-borne diseases.

Having your farmland infested with hard-to-control or uncontrollable soil-borne diseases is financially disastrous.

How clubroot is spread

Ten ways to spread clubroot include the following:

1. Custom field fertilizer equipment — has it been on clubroot-infected cropland?
2. Custom seeding equipment — same as No. 1.
3. Custom harvest equipment — same as No. 1.
4. Do you sell bales of straw? The straw wagon could have come from clubroot-infected cropland.
5. Borrowed equipment — has it been cleaned before you use it?
6. Oilfield service equipment.
7. Powerline installation equipment.
8. Recreational equipment — quads, snowmobiles, etc.
9. Windstorms moving soil from a nearby cultivated field.
10. Renting out your cropland to potato growers.

Bring all of these 10 ways to spread clubroot to a full stop.

Before you get clubroot onto your cropland, bring it to a dead stop. Plant clubroot-resistant canola.

The amount of clubroot fungus spores carried on equipment wheels or that which can be blown onto your cropland is not high if you are able to control the following:

  • Clubroot-susceptible canola.
  • Any weed in the clubroot family, stinkweed or wild mustard.
  • Prevent any equipment entering your land that has not been reasonably cleaned of big mud clods.

The amount of fungus spores (inoculum) that will be brought onto your land will, generally, not be enough to overcome the clubroot resistance of your canola crop.

How clubroot resistance is overcome

Clubroot resistance is overcome when you allow your non-clubroot-resistant canola to become infected. When you have a field of clubroot-infected canola, you end up with millions of clubroot spores per gram. Now you have a problem. When you plant resistant clubroot varieties onto this massive clubroot soil infestation, the resistance of the resistant variety will break down in three to four canola rotations. You now have to look for another resistant variety that will hold up and give you an expected profitable yield, if one is available.

Can you see my reasoning? I know of canola growers in the Edmonton area who are clubroot-free as of today. They went with resistant varieties as soon as was possible, and they kept their crops free of cruciferous weeds and volunteer canola.

I am totally appalled at the rapid spread of clubroot in both Saskatchewan and Manitoba. It’s not inevitable. It’s only inevitable if you do nothing.

Resistant varieties will hold up for many, many years or, perhaps, forever if you follow the above reasoning.

For example, how did clubroot get to the relatively isolated Peace Region of Alberta? It did not blow up or walk up. It was likely carried the long distance from central Alberta on big earth clods on the wheels of farm or oilfield equipment. So, hurry up and plant resistant varieties right now.

If you think that your neighbour has clubroot, check out the field entrances. Does the canola crop look healthy? Perhaps even pull up a few volunteer canola or cruciferous weeds — look for club-shaped roots.

If you’ve got clubroot on your cropland you now have no choice, you must grow resistant varieties. You should — or must — depending on your county, follow a four-year rotation. Your resistant variety may hold up if three to five rotations (four-year rotations) are followed.

If some of your land is clubroot-free

Follow all of the information with respect to clubroot prevention. Treat this clubroot-free land, maybe half of your farm, as a separate entity. Immediately use resistant varieties and follow every precaution. Yes, I know of several farmers doing just this very successfully for the last 10 years or so.

Consider using a steam cleaner for your field equipment and have it installed in your equipment yard. Stay clean and keep clubroot at bay.

Wind blown dust has decreased with zero and minimal till and even though fungus spores may move in the wind, if your fields are free of susceptible weeds and susceptible volunteer canola, clubroot will not get established. Do not try and blame ducks and geese because the amount they may carry on their feet would not be enough to start an infection. Can you prove otherwise?

Prevention is the best form of cure! Remember, in Alberta we have no Dutch elm disease or rats. It’s way less expensive than cutting down elm trees or trying to rat-proof your farm.

About the author

Contributor

Dr. Ieuan Evans is a forensic plant pathologist based in Edmonton, Alta. He can be reached at [email protected]

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